A semiconductor device including an SiP (System in Package) structure in which plural semiconductor chips are stacked and sealed in one package is in practical use to enable a miniaturization and a high function of a semiconductor device. In the semiconductor device of the SiP structure, it is required to transmit and receive electrical signals between the semiconductor chips in high speed. In this case, micro-bumps are used for an electrical connection between the semiconductor chips. The micro-bumps each have a diameter of, for example, approximately 5 μm to 50 μm, and are formed on a surface of the semiconductor chip with a pitch of approximately 10 μm to 100 μm.
When the semiconductor chips are connected by using the micro-bumps, the bumps formed at upper and lower semiconductor chips are aligned with each other, and thereafter, the upper and lower semiconductor chips are pressure-bonded while being heated to connect the bumps with each other. An underfill resin is filled into a gap between the upper and lower semiconductor chips to increase connection reliability and so on. When the gap between the chips decreases excessively at the bump connection time, an excessive crush of the bumps and a short circuit in accordance with the crush occur. Accordingly, it is required to keep the gap between the upper and lower semiconductor chips. Further, if a warp occurs at the semiconductor chip after the bump connection, there is a possibility that a connection failure (open failure) occurs between the bumps. Accordingly, it is required to enhance connection strength between the semiconductor chips before the underfill resin is filled.